The present invention relates to a loading device for a thermal printhead so that the load on the printhead and thus the center of force urging the printhead against a thermal transfer ribbon and a substrate on which printing is to occur is controllable and adjustable.
Identification card printers are well known in the art. Dye sublimation and thermal resin printing technology are used to print a photo realistic image on an identification card or substrate made up of plastic or some similar material such as polyester, polyvinyl-chloride (PVC), or PETG.
In the card printing industry, a standard size card has been used by all printer manufacturers when designing the printers. Hoppers to hold cards, pinch or drive rollers to move the cards through the printer, ribbon size, and lamination stations all are designed with the standard size card size of 2.125 inches by 3.375 inches (known in the industry as a CR-80 size card). Some printers, such as the Fargo Electronics Inc. model 4250 have the capability to handle larger size cards, such as cards in sizes of 2.375 inches by 3.625 (known in the industry as a CR-90 card) and 2.625 inches by 3.875 inches (known in the industry as a CR-100 card).
In order to have good image quality, many factors must be designed into the printer. Printing is accomplished by the printhead pixels being fired or heated under control of an outside computing device. The pixels produce heat, and a dye sublimation or thermal resin ribbon is positioned between the printhead and the identification card. As the pixels are fired and heated, the dye on the ribbon releases from the carrier and is sublimated into the identification card, or in the case of thermal resin ribbon, the heat from the pixels causes the resin to release from the carrier and bond to the surface of the identification card. One of the factors in the design of the printer that must be carefully considered is that the printhead in the printer must maintain a suitable pressure on the ribbon and the card so that a uniform transfer of resin or dye is accomplished. If the pressure on the card is unequal across the width of the card, the heat generated by the firing of the pixels in the printhead will be uneven and will cause the dye to sublimate at uneven rates, which results in a card that is not uniform in terms of the print quality since the ink has sublimated or transferred unevenly. The end users of such cards will not accept such print quality.
Since most printers are designed simply to accommodate one size card, that of the CR-80, the manufacturers of the printer have opted to fix the position where the center of force is applied to the printhead to the center of the CR-80 card. In some cases, this option will also work for the larger CR-90 cards since the overall dimensions are not so significantly different from the CR-80 card as to prevent a reasonably even application of the dyes from occurring. However, this is not the case when the card sizes are smaller and vary from the CR-80 card size more widely than do the CR-90 cards. The present printer has the capability to print on varying sizes of card by permitting lateral adjustment of the center of force application.
The invention described is a mechanism that moves the pressure point of the printhead on a horizontal plane so that it can be adjusted to be flexibly centered on a blank identification card of any size as long as it will fit in the size parameters of the printhead.
The present invention comprises a laterally adjustable mounting for a printhead that permits accurate application of dye sublimation and resin images to a rigid plastic card by insuring that there is an even force distribution over the line on the printhead that engages the card. The mounting permits changing of the lateral position of the center of application of force on the thermal printhead to accommodate centering the force on rigid plastic cards of a variety of widths. The changing of the lateral position of the application force on the thermal printhead optimizes the performance of the thermal printhead printing mechanism for various widths of substrates.